In the past, various mechanical devices have been developed to assist humans in walking, running, or jumping. These devices are normally used for sports or other amusement purposes, or for the aid of persons who are partially disabled. Typically, these devices include mechanical linkage together with springs or other energy control devices to enhance the physical capability of the user's legs. Motion of the legs may be enhanced and assisted in three basic directions; extension and retraction, side-to-side, or fore-and-aft. Some devices are designed for high performance and an enhanced mobility above and beyond that for which an ordinary person would normally be capable. These typically enhance and assist only extension and retraction, with side-to-side and fore-and-aft motions effected more or less directly by similar motions of the user's legs. We concern ourselves primarily with devices of this form. The enhancement may take one of several basic forms.
One type of device links the user's torso to his feet, which engage the ground more or less directly, and acts to enhance the strength of the user's legs by adding to the force that the user applies with his own legs. This first type, then, uses linkage that allows a spring, or other energy control device, to act in parallel with his own legs to enhance their capability. This type of device can recover energy of downward motion of the user and return it, or add to it by means of a primary power source, when he springs up again. It gives the user the advantages of added strength and of safety because the added forces are not transmitted by his legs. Disadvantages are: (1) while leg forces are enhanced, the effective leg extension remains unchanged; (2) unless a means of disengagement is provided, the force provided by the device may prevent user from picking up the foot not engaging the ground and so will prevent a normal walking or running motion. The means of disengagement typically has an all-or-nothing character and is switched on or off depending on some physical condition such as, e.g., which leg is farther forward. Thus, a further disadvantage is that the device is variable in its response and can give unpredictable results in some circumstances. The recent U.S. Pat. No. 4,872,665 by Chareire is an example of this type of device.
A second type of device is mounted to the user's legs or feet, and engages the ground instead of the user's own feet with a varying length that adds to the extension of his own legs. This device is designed to effect a spring action or otherwise enhanced action between the user's feet and the ground. This action acts in series with the action of his own legs to enhance their capability. This type of device is able to recover the energy of downward motion of the user and return it when he springs up again and has the advantage of increased extension compared to the user's own legs. Disadvantage are: (1) while leg extension is enhanced, all of the force must be supplied by his own leg; (2) side-to-side and fore-aft bending moments on the user's knee may be increased due to the extra length, thus increasing the danger to the user; and (3) substantial compression of the spring action for either leg will cause the apparatus for the other leg to tend to drag on the ground due to its extra length and so interfere with a normal walking or running motion. U.S. Pat. Nos. 3,065,962 and 3,110,492 by Hoffmeister are examples of this type of device.
A third type of device combines features of the first two types. It attaches both to the torso and the feet while also at extending with variable length beyond the user's own feet, engaging the ground independently of the user's own feet. With attachment at the torso, an additional force can be applied to add to that supplied by the user's leg, while the variable length extension can increase the leg's extension. Rather than acting only in parallel or in series with the action of the user's leg, this type of device allows springs or other energy control devices to act both in parallel and in series with his leg. This type of device can recover energy of downward motion of the user and return it, or add to it by means of a primary power source, when he springs up again. It offers the user the advantages of added strength and of safety, because the added forces are not transmitted by his legs; also the advantage of increased extension compared to his own legs. A further advantage is that increased side-to-side and fore-aft bending moments and caused by increased leg length may be applied not to the user's knee but only between his feet and torso with the device providing side-to-side and fore-aft rigidity.
A previous example of this third type, U.S. Pat. No. 406,328 by Yagn, uses a particular form of parallel and series connections involving two separate springs for each leg. In this case, one spring was arranged to act between the user's foot and a ground-contacting element while a second acted between the torso and the ground-contacting element. This device uses one spring in series with the user's leg while the second acts in parallel with the leg and also with the first spring. Disadvantages of this example include the problems of both of the first two types of device relating to foot dragging and foot raising. When raising a foot in order to take a step, the spring attached to the torso acts to prevent the foot from raising, and so a means for alternately engaging and disengaging that spring was implemented. The lack of flexibility and predictability inherent in such a system is a serious disadvantage. For example, the torso spring must surely disengage or the leg cannot be picked up, and the spring must surely engage or the expected spring force is missing. Additionally, foot dragging limits the performance of this device, by limiting the compression which is acceptable between the foot and the ground for the load bearing leg to an amount the user can compensate by lifting high his other foot.
The present invention also provides a human mechanical bipedal device of the third type described above. It differs from the previous example in ways that address and eliminate the disadvantages relating to foot dragging and foot raising while preserving the advantages for devices of this third type. Its primary distinguishing features are:
Firstly, the mechanism for each leg effects a lever action with mechanical advantage greater than 1:1 in series with a spring action. The lever action increases the force exerted by the user's leg while the spring action enhances its extension. Requiring only one spring, such a mechanism effects spring action both in series and in parallel with the user's leg. The increase in force generated by the leverage action is transmitted directly between the ground and the user's torso, for increased strength while the spring action in series with his leg acts to allow increased extension. In contrast to previous examples of the first and third types, this action allows the user to freely pick up his foot at any time, and so can be engaged at all times for greater safety, predictability, and flexibility of operation.
Secondly, a common main spring is used for the two legs which act on it in parallel to allow compression of the two legs to be coordinated and so prevent foot-dragging induced by substantial compression of one leg against the ground. Together with the action described in the previous paragraph, a leveraged action for each leg is provided which acts in series with a common main spring. Thus, if either leg is raised, the device for that leg will be raised above the ground with respect to that for the other leg irrespective of any compression allowed by the spring action.
This new device has all of the advantages described above for devices of the third type. They make possible higher performance than would otherwise be possible together with flexibility and predictability of operation. Safety is also enhanced due to protection of the user's leg and leg joints from increased forces and bending moments. Additionally, use of a single spring used alternately by the two legs reduces the weight associated with a large spring element with high energy storage capacity. With the spring element carried on the user's back, the weight of the legs is reduced for increased agility. A disadvantage is that without added power and with legs longer than the user's legs, their response to foot pickup is smaller than that of his own leg due to the effects of leverage, which adds difficulty in negotiating uneven terrain and hampers recovery when falling.
Large jumps off either or both feet are made possible by this invention, as are large jumping steps with an otherwise normal walking or running motion. To achieve these objectives, a number of problems must be overcome. The device must balance or distribute lift forces acting on the body to prevent undue force on the body so the device is safe and manageable and will not prevent a normal walking or running motion. Since the device adds weight to the body of the user, it must be reasonably light in weight so that undue fatigue will not become a problem with extended use. The device should also respond quickly to bodily movements and not prevent running or walking with a normal motion. It should also allow normal fore-and-aft and side-to-side motion of either leg. Undue shock forces should also not be transferred directly to the body of the user. In addition, impact forces should not place undue stress on the body such as the knee joints, for example.
The human bipedal device of this invention overcomes problems by providing enhanced walking, running, or jumping over various types of terrain with a natural motion characterized by controlled trampoline-like jumps. By way of example, one embodiment of the device allows the user to jump four or five feet vertically with both legs, or single leg jumps about two to three feet off the ground. In addition to its uses as a sports, exercise, or amusement device, the invention also can be used for producing special effects in the entertainment industry and also has military applications.
A short discussion of mechanical aspects follows: The mechanical advantage of the lever action in series with the spring action is defined with respect to the motion and force of the user's foot in extension and retraction in relation to the resultant motion and force of the device against the ground, i.e., a mechanical advantage of 2:1 will generate a force against the ground which is twice the force of the user's foot against the device, while extension of the user's foot will extend the device against the ground by half as much. Attachment to the torso makes possible such a lever action since the extra force against the ground above and beyond that supplied by the user's leg and which is required by this action may then be transmitted from the user's torso. The role of the mechanical advantage in determining the series/parallel nature of this device can be seen by examining two extreme cases. For a mechanical advantage of 1:1, no additional force would be added to that provided by the user's leg, and the spring would act purely in series between the user's foot and the ground. Alternatively, a very large mechanical advantage, say 1000:1 would free the user's legs while placing the spring action between the torso and the ground, in parallel with any force that the user's foot might exert due to touching the ground directly. It is worth mentioning that all realizations of a lever action in series with a spring action are functionally equivalent, irrespective of where the spring or springs are placed in the mechanical circuit. Only the particular nature of the lever action needs to be clearly specified. By action in series is meant the usual definition of mechanical action in series, so that forces in both lever and spring are equal, except for constants of proportionality determined by the mechanical advantages of the constituent parts, while the extensions due to lever and spring motion are algebraically added.